Abstract
The role played by dopamine D1 and D2 receptors in formalin test analgesia was explored by challenging D-amphetamine- and morphine-induced analgesia with mixed and selective D1 and D2 antagonists, and by examining the relative analgesic activity of mixed and selective D1 and D2 agonists. The mixed D1/D2 dopamine antagonist cis-flupenthixol (0.5 mg/kg), the D2 antagonist pimozide (0.5 mg/kg), and the D1 antagonist SCH 23390 (0.1 mg/kg) attenuated both D-amphetamine and morphine analgesia. The mixed D1/D2 agonist apomorphine and the selective D2 agonist quinpirole produced dose-dependent analgesia while the selective D1 agonist SKF 38393 was without effect. These data suggest that D1 receptors play an "enabling" role in D2 receptor-mediated analgesia in the formalin test.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / pharmacology
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Analgesia*
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Animals
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Apomorphine / pharmacology
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Benzazepines / pharmacology
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Dextroamphetamine / pharmacology
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Dopamine Agents / pharmacology
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Dopamine Antagonists
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Dose-Response Relationship, Drug
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Ergolines / pharmacology
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Flupenthixol / pharmacology
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Formaldehyde
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Male
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Morphine / pharmacology
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Pain / chemically induced
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Pain / physiopathology*
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Pimozide / pharmacology
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Quinpirole
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Rats
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Receptors, Dopamine / drug effects*
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Receptors, Dopamine D1
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Receptors, Dopamine D2
Substances
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Benzazepines
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Dopamine Agents
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Dopamine Antagonists
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Ergolines
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Receptors, Dopamine
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Receptors, Dopamine D1
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Receptors, Dopamine D2
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Formaldehyde
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Pimozide
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Quinpirole
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2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine
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Morphine
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Flupenthixol
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Apomorphine
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Dextroamphetamine